1. Field of the Invention
The present invention relates to the field of methods and systems for manufacturing and testing integrated circuits using probe cards or other probe elements; and more particularly the present invention relates to the field of cleaning and reusing probes used in such manufacturing and testing.
2. Description of Related Art
During manufacturing of integrated circuits, devices known as probe cards are used to test the characteristics of a fabricated integrated circuit chip formed on a semiconductor wafer. Probe cards comprise a circuit board (or other structure) and an array of probe wires connected to test circuits on the circuit board. The probe wires are arranged so that the tips line up with contact pads on the chips to be tested. The probe card is positioned to cause electrical contact between the test circuits and the pads on an integrated circuit on the wafer.
To test the integrated circuits on a wafer, the probe card typically is set into an integrated circuit testing machine, and wafers containing integrated circuits are placed in the machine below the probe card. The probe card is placed to cause contact of probe tips on a selected circuit on the wafer, and tests are executed. It is important that the probe tips of the probe needles of the probe card make accurate and good electrical connection with the contact pads of the circuit under test. To achieve good and accurate connections, it is important that the needles be properly aligned and that the probe tips be clean and electrically conductive.
For a discussion of probe cards, see U.S. Pat. No. 4,864,227, invented by Mitsuya Sato, entitled WAFER PROBER. For a discussion of wafer probing equipment, see U.S. Pat. No. 5,525,912, invented by Tomomi Momohara, entitled PROBING EQUIPMENT AND PROBING METHOD.
During use, probe tips of the probe cards accumulate debris, which increases contact resistance and otherwise degrades performance of the probe card. According to one prior art technique, probe cards are cleaned using a solvent while an operator views the probe cards under a microscope and cleans the probe tips individually. Other prior methods used mechanical scrubbing of probe tips to remove debris. Such methods are time consuming and subject the probe tips to misalignment and wear.
It is therefore desirable to clean probe tips in a way so as to allow for reuse of the probe cards, minimize the damage to the probe tips, and reduce risk of misalignment of probe tips. Also, it is desirable to allow probe cards longer life and to reduce interruption of integrated circuit manufacturing due to replacement of probe cards.
Thus, there is a need for an improved method of cleaning probe cards.
The present invention provides a method of cleaning an electrical contact. The electrical contact is used for contacting an integrated circuit and accumulates debris during use. The method comprises directing electromagnetic radiation at the contact. The electromagnetic energy reacts with at least one of the contact and the debris so as to cause at least a portion of the debris on the contact to be removed.
The electromagnetic radiation may comprise coherent radiation, such as electromagnetic radiation generated using a laser. The portion of the debris may comprise organic debris, aluminum oxide, polyimide, silicon dioxide, nitride, or other debris. According to one aspect of the invention, the contact comprises a conductive material and the electromagnetic radiation causes removal of the portion of the debris substantially without removal of the conductive material. According to another aspect of the invention, the electromagnetic radiation at least partially melts the conductive material.
The wavelength of the electromagnetic radiation is selected to remove debris. In one system, the wavelength is selected to bring contact resistance of the probe tip below 2 Ohms. In another system, the wavelength is selected to bring contact resistance of the probe tip below 5 Ohms. The electromagnetic radiation may comprise a wavelength in the ultraviolet range of the electromagnetic spectrum, or alternatively, a wavelength in the green range of the electromagnetic spectrum.
The contact has a diameter and the electromagnetic radiation comprises a beam of energy, where the beam has a diameter greater than the diameter of the contact. In one system the contact has a diameter less than 45 microns and the electromagnetic radiation comprises a beam of energy capable of removing debris, where the beam has a diameter greater than 25 microns.
In one preferred system, the contact comprises a probe tip. In such a system the probe tip may comprise the tip of a probe needle mounted to a probe card used for testing integrated circuits.
The invention provides a method of cleaning a probe tip on a card including placing the card into a probe card analyzer and, while the card is in the probe card analyzer, directing electromagnetic radiation at the probe tip. The electromagnetic energy reacts with at least one of the probe tip and the debris so as to cause at least a portion of the debris on the probe tip to be removed. A test is executed on the probe card while the probe card is in the probe card analyzer. Based on the test, it is determined whether to direct radiation at a second contact on the card. According to another aspect of the invention, resistance of a second contact on the card is measured, and electromagnetic radiation is directed at the second contact if the resistance is outside a particular operating range for probe tips. The particular operating range may be between 0 and 1 Ohm, between 0 and 250 miliohms, between 0 and 100 miliohms, or other range or subrange.
The invention provides a device for cleaning electrical contacts on test cards which comprises a source of electromagnetic radiation, optics optically coupled to the source of electromagnetic radiation, and a test card holder. The test card holder is positioned relative to the optics allowing electromagnetic radiation from the source of electromagnetic radiation to be directed onto a contact on a test card positioned in the test card holder. According to an aspect of the invention, the contact comprises a probe tip and the test card comprises a probe card.
The device, according to one aspect of the invention, comprises a movable stage coupled to the card holder movable to position the contacts on the card relative to the optics. Further, the device may comprise a display for viewing the probe tips coupled to the optics. According to another aspect of the invention, the source of electromagnetic radiation comprises a laser, such as a gas or solid state laser. The laser may be one of various types such as a xenon laser, CO2 laser, nitrogen laser, excimer laser, or frequency doubled or tripled Nd:YAG laser.
The present invention provides a process of manufacturing integrated circuits which includes fabricating a plurality of integrated circuits and contacting pads of the integrated circuits with a plurality of electrical contacts which accumulate debris during use. The integrated circuits are tested using the plurality of electrical contacts and packaged. Electromagnetic radiation is directed at at least one contact in the plurality of electrical contacts and reacts with at least one of the contact and the debris on the contact to cause at least a portion of the debris on the contact to be removed. A second plurality of integrated circuits is tested using the plurality of electrical contacts and packaged.
The invention includes a semiconductor testing device including a source of electromagnetic radiation directable to at least an electrical contact among the electrical contacts on the device. The device includes test electronics, a test card coupled to the test electronics. The test card includes electrical contacts that accumulate debris during use. The device also includes a semiconductor holder positioned relative to the test card.